Process for making railway sleepers



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IN VEN TOR. flc/o a 777azza BY United rates Patent PROCESS FOR MAKING RAILWAY SLEEPERS Adolfo Mazza, Genoa, Italy Application June 14, 1951, Serial No. 231,527

1 Claim. (Cl. 92--54) In my Patent 2,169,704 I have described a railway sleeper which is made with a plurality of superposed sheets of cement-asbestos; said sheets are manufactured from a mixture of cement, asbestos and water with a process similar to the process employed for making cardboard and the resulting material is commonly known by the trade name Eternit.

According to the previous method, these sleepers were manufactured by assembling the aforementioned sheets, between which metal reinforcements were embedded, and then compressing the resulting body keeping it under a suitable pressure until sufliciently hardened.

Such prior practice involved the use of expensive equipment and particularly a considerable number of molds, because the sleepers had to be kept in said molds in a compressed condition for at least 24 hours due to the tendency shown by said laminated cement-asbestos material to swell and even to crack if the pressure were removed when the material was still in the fresh state.

The object of the present invention is to provide a process for making sleepers of the kind specified abOve, in which each sleeper is removed from the mold immediately after being compressed, so that the necessity of occupying a great number of expensive molds is eliminated.

Another object of the invention is to obtain sleepers of cement-asbestos from which a greater portion of water is eliminated whereby a greater stifiness and strength of said sleepers is obtained.

A further object is to provide a quicker process for making such sleepers, so that a greater output can be attained with less labor.

It has been found that when a great number of superposed fresh Eternit sheets are strongly pressed together, the water contained therein cannot find its way out pass? ing through the layers because the latter, when they are compressed beyond a certain stage, act as waterproof walls contrasting the passage of water therethrough.

As a consequence, it was neither possible to exceed a pressure of about 400 kgs. per square cm., nor to relieve such a pressure immediately after compression without the danger of the sleepers cracking due to the excessive pressure of that portion of water which remained enclosed within the cement-asbestos layers. 1

This difliculty has been now overcome by providing an exceedingly rugged mold with perforated or slotted sides in which the layers of the cement-asbestos material are placed one upon the other; and then by exerting a progressively increasing pressure on said layers, the excess water contained in the mixture finds its way between adjacent layers towards said perforated wallsand can flow out through the aforementioned perforations.

It has been found that by this process it is possible -to compress the material at a pressure up to 600 kgs. per

square cm. or even more, whereby almost all of the excess water is pressed out and a more compact and strong sleeper is obtained. A further important feature ice 2 is that the sleeper may be compressed to athickness which is less than the final thickness required, so that by removing the same from the mold immediately and leaving it to season and dry'without keeping in a compressed condition, it partially swells up to the greater final thickness desired, with no danger of cracks being formed in the sleeper.

A particular manner of proceeding for manufacturing sleepers according to my present invention will be here inafter described with reference to the attached drawings, wherein:

Fig. 1 represents in expanded relation the layers for making a sleeper;

Fig. 2 represents the finished Sleeper;

Figs. 3 and 4 and 5 show steps in the preparation of the pile of sheets forming the sleeper;

Fig. 6 is a longitudinal ection of the pressing machine;

Figs. 7 and 8 are cross sections of the pressing machine in two different stages of operation;

Fig. 9 shows a detail of Fig. 7 on a larger scale;

Fig. 10 is an enlarged perspective view showing the structure of the mold walls;

Fig. 11 is a modification of Fig. 9.

For making the sleepers according to my invention, the starting material is the one used for making the well known Eternit sheets, that is a suspension of asbestos or like fibres, Portland cemen and Water in a conventional paper beater. The proportions of the materials are preferably about 1 part by weight of asbestos to 6.5 parts by weight of cement. These proportions may vary, however, within comparatively wide limits.

The suspended materials are picked by a moving belt which is passed through the suspension in a suitabletank.

The belt is passed against a collecting drum and trans fers thereto, in the form of a thin layer, the material picked up from the suspension,

' The process is repeated until the material on the drum forms a sheet of adequate thickness.

The weight of the drum provides moderate compression on the soft laminae successively applied thereto to compress them into a wet self-sustaining sheet. The sheet is then removed from the drum and straightened out. The water content of this sheet is about 30 per cent.

All this first stage of the process is conventional and well known long since in the art, for instance from the U. S. Reissue Patent No. 12,594 to Hat'schek reissued January 15, 1907. The aforesaid sheet, about 6 mm. thick, is cut into pieces 1 (Fig. 1), some of which are about 24 cm. wide and 230 cm. long, the others having the same width and a length varying from to cm. These sheets are superposed to form a pile in the order as shown in Fig. 1 on a supporting plate 2 having an arched middle portion, such plate being placed on the table 3 shown in Fig. 3.

The table 3 is surrounded by a frame 4, provided with hand grips 5, which frame can slide up and down on the sides of the table 3 and can be supported in the elevated position by the tiltable arms 6 as shown in Fig. 4. When the frame is in this latter position, the sheets 1 are laid upon the plate 2, within the frame 4, in the order shown in Fig. l, whilethey are being moderately compressed by h Metal reinforcements and metal anchoring elements are inserted in the proper positions in the pile during this op on h his pre mina m i ope on is completed, the frame 4 is lowered again and the plate 2 w t th haped pi f sh 1 is emove from the table 3 by any suitable means 7 and is transported on the slide support 8 of the pressing machine shown in Fig. 6.

For instance, for making a sleeper 230 cm. long, 24 cm.

wide and 14 cm. thick, 31 sheets are piled up and slightly compressed by hand on the plate 2;'the thickness of each sheet being 6 mm., the total thickness of the resultant pile of sheets is about'l8 cm. The total weight of the fresh material is 186 kgs., the water content being about 55 kgs. This comparatively high contentof water is a consequence of the process of manufacture 'of ,Etcrnit sheets as described above.

The pressing machine shown diagrammatically in Figs. 6 to 10 comprises a frame including hydraulic cylinders 10in which pistons 11 are actuated by a compressed fluid by any suitable means through the duct 12.

' The pistons 11 sustain a support piece 13 having a plane top surface which, when the support piece 13, is completely lowered on the cylinders 10 is at the same level as the slide support 8 mentioned above.

The upper portion of the support13 has the same length and width of the plate 2 and is closely surrounded by an annular'inold 14, the structure of which will be described in detail further on. The annular mold '14 is provided with rods 15 passing through the top member of the frame 9 and connected to'a plate 16 fastened to a piston 17 contained in a hydraulic cylinder 18 provided with an aperture 19 for introducing a compressed fluid therein and discharging it therefrom. The cylinder 18 is rigidly connected to the frame 9 by means of rods 20 loosely passing through holes in the plate 16.

The annular mold 14 rests on two pistons 21 contained in two hydraulic cylinders 22 at the ends of the machine (Fig. 6), provided withapertures 23 for a compressed fluid. When the annular mold 14 is in its lowermost rest position, the top surface of the sides thereof is at a level which is slightly higher than the top surface of the support piece 13, e. g. one centimeter higher.

A piece 24, having the same length and width of the support 13 projects downwardly from the top member of the frame 9.

A slide support 25 is provided at the opposite end of the machine with respect to the similar support 8.

The structure of the annular mold 14 appears from Figs. 9 and 10.

The inner surface of this mold is formed by the faces of a plurality of staves 26; these staves are inserted in dovetail fashion into the body of the mold 14 and each of them has a side face slightly recessed as shown at 27, Fig. 10, whereby the inner face of the mold shows a series of thin slots; behind the staves 26 a cavity 28 is provided in the body of the mold, which is connected'to an outlet conduit 29.

According to the modification shown in Fig. 11, the body 13 is made with a recess 31 in which a longitudinal partition 32 of the annular mold 14 penetrates so that two sleepers at a time can be obtained.

The operation of the machine is the following: 7

The plate 2 with the superposed pile of sheets 1 placed on the slide support 8 is pushed forward, or conveyed by any suitable power means, onto the upper surface of the support piece 13; the plate 2 slides on this surface as being guided by the sides of the annular mold 14, slightly projecting over the top of the support piece 13 as explained above (Fig. 7).

When the plate 2 with the sheets 1 lies entirely on the support piece 13, the annular mold is caused to rise by means of the pistons 21, so as to enclose the pile of sheets 1. At this stage, corresponding to the position shown in Fig. 8, fluid under pressure is gradually fed into the cylinders 10 whereby the pistons 11 are lifted and the support piece 13 gradually compresses the pile of sheets 1 against the top piece 24.

As the compression increases, water is squeezed out through the sides of the pile of sheets 1 and finds its way When a pressure of about 400 kgs. per sq. cm. on the sheets is reached, the pile is reduced to a thickness of 14 cm., which is the thickness required for the finished sleeper; the pressure in the cylinders 10, however, is further increased and brought up to about SOO kgs. per sq. cm;

The time involved for reaching this pressure is about 10 minutes, for allowing most of the water to be expelled to issue from between the compressed layers of the laminated cement-asbestos body.

At the last mentioned pressure the thicknessof the cement-asbestos body is reduced to about 13.5 cm. and a further quantity of water is squeezed out therefrom.

The pressure in the cylinders 10 and 22 is then released andat the same time compressed fluid is introduced in the cylinder 18, whereby the piston 17 forces the annular mold down to the initial position shown at Fig. 7.

The sleeper is thus extracted from the mold and can be pushed forward, together with the supporting plate 2, onto the slide support 25, by the next following plate carrying another pile of sheets placed on the slide support 8, with the intermediary of a wooden spacer The sleepers thus produced, are stored for setting and ageing and during the first period after their compression they slightly swell reaching a thickness of 14 cm.',which is the final thickness desired. .1

The loss of water due to the gradual compression is 27 liters compared to 55 liters. initially contained in the fresh sheets, the weight offthe sleeper extracted from the press being 159 kg. jThe weight of the same sleeper after90 days is 154 kgi' As it is-obvious, the, figures mentioned above, relating to the dimensions of the sleeper, proportion of ingredients, number of layers, pressure and duration of thepr'oc ess, as well as the details of the machine can vary, still remaining within the scope of the invention as defined by the appended claim.

This application is a continuation-in-part of application Ser. No. 786,325, filed November 15, 1947, now abandoned. I 1 I Having now particularly described and ascertained the natureof mysaid invention and in what manner the same is to be performed, I declare that what I claim is:

A process for making railway sleepers of a predetermined thickness comprising introducing a plurality of separate superimposed sheets of a wet laminated mixture of cement asbestos -in direct contact with one another forming a single body in a suitable mold, compressing said body in a direction perpendicular to said sheets with a pressure gradually increasing through a period of time moving the compressedbody from the mold and leaving out through the slots 27, cavity 28 and outlet conduit 29.

said body to season into a hardened sleeper.

References Cited the file of this patent UNITED STATES PATENTS 504,730 Lane Sept. 12, 1893 515,958 Hubbard Mar. 6, 1894 7 698,948 Heyl Apr. 29, 1902 868,996 Kemp Oct. 22, 1907 1,949,472 Hopkinson Mat. 6,1934 2,079,664 'Seigle May 11, 1937 2,080,285 'Maclldow ie May 11, 1937 2,082,399 Isman et al June 1, 1937 2,169,704 Mazza Aug. 15, 1939 2,171,155 Wright Aug. 29, 1939 2,568,023

Perry Sept. 18, 1951 

